An electro-mechanical transmission includes a gear set that interconnects one or more electric devices and a final drive of the vehicle, e.g., an axle, wheels, etc. The gear set changes rotational speed and torque that is output from the electric devices, and delivers it to the final drive. The transmission may further be configured to receive torque from another power source, such as but not limited to an internal combustion engine. The transmission must also change the rotational speed and torque that is received from the engine, and provide it to the final vehicle drive system. One or more of the electric devices may be operated simultaneously with the engine, or may operate with the engine turned off and disconnected from the system, in order to provide a tractive power for the vehicle.